Ironworking in Roman Britain

A variety of metals was mined and used by the Romans, including
copper, gold, silver, lead and iron. Ironworking was widespread in
Britain by the later Iron Age. In fact, iron was listed as a
British export by the Greek author Strabo shortly before the Roman
invasion. With the incorporation of Britain into the Empire
large-scale production was achieved.

Ores were available in most parts of the country and iron became
the cheapest metal, and was used for a diverse range of fittings
and objects. Most blacksmiths probably bought their raw material
from smelters, in the form of ingots or rods. Another source was
scrap metal; broken or worn iron objects would be taken to the
smith for re-forging.

Unlike other metals, iron was not cast in the Roman period.
Instead, the blacksmith forged it in a semi-solid, red-hot state
using hammer and tongs. Thin iron sheet was joined with rivets, but
the normal joining technique was welding at white heat. Various
hardening techniques were known, and steeled cutting edges were
sometimes welded to tools and weapons. Few of these techniques were
new, and it was not the case that a poor Iron Age technology was
replaced by a superior Roman one. Rather, existing skills were
adapted to changed circumstance, notably a new, highly-organised
trading network.